The nucleic acid (RNA) isolated from the 20nm particle found in P147 and "poky" is to be characterized. The base ratio should tell us if it is single-or double-stranded while polyacrylamide gel electrophoresis should tell us if we are working with a multicomponent virus system. The sedimentation of the 20nm particle from strains P147 and "poky" in sucrose density gradients suggests that morphologically identical particles do in fact differ. With our new method for getting around the "polysaccharide" problem in Neurospora extracts, we are going to reinvestigate "poky" to determine whether there is a second VLP in this strain. We know there is a second particle in the P147 strain, but the "polysaccharide" has frustrated our previous attempts at purification. We plan to extend our investigation of the N. crassa mi-3 mutant which seems to carry the 20nm particle characteristic of strains P147 and "poky" as well as an additional larger particle. We have been selecting slower growing strains from "poky" with the idea of seeing whether slower growth correlates with enhanced VLP content per mg extractable protein. The fourth cycle of selection has just been completed and extraction for VLP's is now in progress. While we complete our nucleic analysis and survey of maternally inherited Neurospora strains, physiological parameters of "poky" are being examined. We have preliminary evidence that "poky" is resistant to blacklight while exhibiting normal sensitivity to shortwave UV. One possibility is that some endogenous photosensitizer is defective in "poky." The investigation of this resistance will be extended as a side issue to our primary objective, the physical characterization of VLPs. In collaboration with another laboratory, we have developed mutant strains of Penicillium chrysogenum to transmit the P. chrysogenum virus (PCV) via heterocaryosis. One strain is virus-free while the other contains abundant VLPs. If heterocaryons form, then we can reisolate strains carrying markers present in the virus-free strain and establish whether virus is present. BIBLIOGRAPHIC REFERENCES: Blanc, P.L., R.W. Tuveson, and M.L. Sargent. 1976. Inactivation of carotenoid producing and albino strains of N. crassa by visible, blacklight, and ultraviolet radiation. J. Bact. 125 (in press).